RFR: 8263995: Incorrect double-checked locking in Types.arraySuperType() [v2]

[Aleksey Shipilev]

On Mon, 22 Mar 2021 18:31:01 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Drop synchronization and volatileness
>
> I'm a bit surprised to see use of volatile/synchronized here as I'm pretty sure that javac is *not* thread safe.
> It seems like the synchronized block has been there from a long time (e.g. it was there since the dawn of OpenJDK :-)). I wonder if a better fix would be simply to drop synchronization and volatileness.

> I'm a bit surprised to see use of volatile/synchronized here as I'm pretty sure that javac is _not_ thread safe.
> It seems like the synchronized block has been there from a long time (e.g. it was there since the dawn of OpenJDK :-)). I wonder if a better fix would be simply to drop synchronization and volatileness.

Yeah, I just did the most obvious semantics-preserving thing in this first patch. See new commit that drops `synchronized` instead as to not confuse both humans and tools about this. Still passes `langtools:tier1`.

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PR: https://git.openjdk.java.net/jdk/pull/3129